Why monogamy?
Creationists and evolutionists don’t agree on much, but they both believe that monogamy is the most stable form of reproduction for the human species. Some nesting birds, voles, and a few other animals are monogamous, but most mammals reproduce with one dominant male controlling a large harem of females. Polygamy seems “natural,” monogamy “supernatural.”
Evolutionary scientists claim that pair-bonding (as in a monogamous marriage) is part of the “deep structure” of human reproduction that humans have evolved as their best strategy for survival and success. So, what are the factors that would commend monogamy?
a) Unlike most other animals, humans crave sex all the time, especially when young and most fertile. They don’t have a short rutting or mating season, followed by a long period of sexual quietude.
b) Unlike most other animals, human babies are born weak, fragile, and utterly dependent for many years. They are not ready to run, swim, or fly away upon birth or shortly thereafter. They need food, shelter, clothing, and education. Most human mothers struggle to care for their children on their own, especially if they already have several other children. They need help, especially from the fathers of the children.
Most fathers will bond and help with a child only if they are certain of their paternity. Experiments have shown that if you put a baby in a crib on a street-sidewalk, most women will stop to look at the baby out of natural empathy, but most men will walk by or walk away, unless they are unusually charitable. Once assured of their paternity, however, most men will bond deeply with their children, help with their care and support, and defend them at great sacrifice. Why? They will likely consider their children as a continuation and extension of themselves, of their name, property, and teachings, of their own bodies and beings, of their genes.
c) Unlike virtually all other animals, humans seem to engage in species-destructive behavior in pursuit of their own sexual gratification.
Evolution therefore appears to strongly favour humans to develop enduring and exclusive sexual relationships, call it as marriages, as the best form and forum of sexual bonding and reproductive success. Monogamous marriages are designed to ensure that both fathers and mothers are certain that a baby born to them is theirs. They ensure that husband and wife will together care for, nurture, and educate their children until they mature.
Of course, polygamy might ensure paternal certainty. While a polygamous man usually has his sexual needs met, his multiple wives often do not, producing rivalry and discord in the home. While a polygamous father may know who his children are, his children have to work hard to get his attention, affection, and resources which are dissipated over multiple wives and children.
But the reality today is that people, encouraged by a permissive society/sexual revolution, have sex and children without marriage. The modern social welfare state has helped to buffer and spread out the costs of this “species-destructive” sexual and reproductive behavior. With many Western societies in economic doldrums, how long that support will last is anybody’s guess.
